> not. This usually indicates a bad guess for Newton. I would now advocate
Oh, did I forget to mention, that other initial conditions DO converge. The funny thing is the initial condition which does NOT converge is actually CLOSER to the solution than ones which DO. Had it been the other way around, I probably would not have thought twice of it. > 1) Grid sequencing: This is easy if you use a DMDA. You just use > -snes_grid_sequence > and its automatic. Since you report that smaller grids converge, this > is usually enough. Unfortunately, no. > 2) NPC: If the above fails, I would try preconditioning Newton with GS. > You can do this > just using multiplicative composition, or left preconditioning. I'm not sure what you mean here. Do you mean I should run normal newton line search snes with SNESSetNPC(snes_of_type_gs)? If so, does the inner snes_of_type_gs and the outer snes_of_type_newtonls get all the same routines? I guess so, but just checking. > If 1 works, then its likely that FAS would work even better. I wish it was so easy: I did try all the snes types before posting the first post. Also all KSP types. Except those that need things I don't have, of course. Cheers, Juha
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